In order to obtain a flat rolled product, it is necessary that the cylindrical rolls used to roll the product have a particular profile, generally having a slight crown in the center and a slight taper towards the ends. It is therefore important to be able to accurately measure and record the variations in the diameter of the roll from one end to the other. Since at least the mid-1930's, saddle micrometers have been used to measure the profile of rolls for flat rolled products. A typical saddle micrometer consists of a wheeled saddle with arms extending down either side of the roll, with a counterweight/follower probe on one arm and a measuring device on the other, so that the saddle can be skated along the roll and differential measurements can be taken across the diameter of the roll where needed.
In recent years, saddle micrometers have been augmented with electrical measurement devices. The mechanical micrometer probe has been replaced with a distance transducer which allows measurement of changes in the roll diameter electronically. The data is processed to calculate location and magnitude of the maximum and minimum diameter of the roll and of the taper and crown of the roll's profile.
Notwithstanding these improvements, all saddle micrometers, from the 1930's to the present, have suffered from a major problem--the measuring arms cannot record diameter at the extreme ends of the rolls because the skate will fall off the roll. Saddle micrometers currently in use attempt to avoid this problem by attaching the measuring arm assembly so that it can slide from one end of the saddle to the other. (See, e.g., West German Patent No. 2,307,824). For example, when the saddle micrometer is at the far left end of the roll, the measuring arm assembly is slid to the far left side of the saddle, so that a measurement can be taken across the diameter of the far left end of the roll. At some point as the micrometer is skated along toward the right end of the roll, the measuring arm assembly is held stable and the saddle is moved underneath the measuring arm assembly so that the measuring arm assembly winds up on the far right side of the saddle, so that when the micrometer reaches the far right end of the roll, a measurement can be taken across the diameter of the far right end of the roll.
This readjustment procedure is unsatisfactory because the accuracy and repeatability of the measurements depend on the care and skill of the operator. The operator must hold the measuring arms stable relative to the roll while moving the saddle underneath the measuring arms. This readjustment can be extremely difficult, particularly on larger rolls, where the skate may be difficult to reach and, due to its size, may be hard to handle. This process is subject to error because the measuring arms are inevitably moved to a slightly different place on the roll. Moreover, there are minor changes in the perpendicularity of the measuring arm assembly to the center line of the roll, which usually results in an irregularity in the recording of the roll profile. This irregularity can result in inaccurate calculations of vital measurements, such as the location of the true crown of the roll and the profile of the roll. Although these inaccuracies are slight, modern quality control standards require that the roll profile be extremely accurate to permit production of large sheets of flat rolled product with a highly uniform, predetermined thickness. In addition to the inaccuracy created by repositioning the measuring arm assembly, this readjustment is time consuming.
This invention responds to the long-felt need for a device which permits a true end-to-end measurement and accurate profile of a roll and which can be taken in a minimum amount of time by an operator with little or no special training.